1. Field of the Invention
The present invention relates generally storage device controllers, and more particularly to streamlining data flow in storage device controllers.
2. Background
Conventional computer systems typically include several functional components. These components may include a central processing unit (CPU), main memory, input/output (“I/O”) devices, and streaming storage devices (for example, tape drives) (referred to herein as “storage device”). In conventional systems, the main memory is coupled to the CPU via a system bus or a local memory bus. The main memory is used to provide the CPU access to data and/or program information that is stored in main memory at execution time. Typically, the main memory is composed of random access memory (RAM) circuits. A computer system with the CPU and main memory is often referred to as a host system.
The storage device is coupled to the host system via a storage device controller that handles complex details of interfacing the storage devices to the host system. Communications between the host system and the controller is usually provided using one of a variety of standard I/O bus interfaces.
Conventionally, when data is read from a storage device, a host system sends a read command to the controller, which stores the read command into the buffer memory. Data is read from the device and stored in the buffer memory.
Typically when data enters the controller from an interface (for example, the “SCSI interface”), the data is MODN aligned (for example, MOD2]. The storage controller includes a buffer memory controller that moves data with a specific alignment, for example, a MOD4 alignment. Hence data must be padded such that it complies with the MOD4 alignment.
In addition, when data is moved from a buffer memory of the controller to the SCSI interface, it has to be re-aligned so that the SCSI interface can send the data out. For example, MOD4 aligned data must be re-aligned to MOD2 data so that it can be read from buffer memory.
Conventional controllers do not provide an efficient system for padding or removing the pad for efficiently transferring data.
Therefore, there is a need for a system to efficiently pad/remove the pad for moving data to/from a controller.